The potential of materials derived from natural sources are being extensively investigated, as they find many applications.
Cellulose fiber is the most abundant renewable material. It contains amorphous and crystalline domains. The acid hydrolysis of cellulose fiber disrupts its amorphous domains and releases individual rod-like rigid crystallites called nanocrystalline cellulose (NCC) that possess high mechanical strength. It is known that the treatment of native cellulose with sulphuric acid introduces negative charges to its surface due to the formation of sulphate ester groups. Since the first discovery of NCC in 1949 by Rånby (Rånby G. Fibrous macromolecular systems cellulose and muscle: the colloidal properties of cellulose micelles. (1951) Discuss Farday soc, IV(111), pp 158-164), interest in this system has risen particularly over the last decade because of its availability, high surface area and aspect ratio. NCC is also practically non-toxic, biocompatible and biodegradable which makes it a potential candidate for several applications.
Chitosan (CS) is produced from partial deacetylation of chitin, the second most abundant biopolymer in nature. Two marine crustaceans (shrimp and crabs) are the main sources of chitin. CS is an amino polysaccharide that possesses positive charges in acidic media due to the protonation of its amino groups. CS is also practically non-toxic, biocompatible and biodegradable. In pharmaceutics, CS has been widely used as a coating material, disintegrant, tablet binder and a vehicle for peptide and gene delivery. In addition, CS has antimicrobial, haemostatic, wound healing, and mucoadhesive properties (see Sonia, T. A., & Sharma, C. P. Chitosan and Its Derivatives for Drug Delivery Perspective. Advanced Polymer Sciences, (2011) 243(April), pp 23-54). Due to its bioadhesive properties, it is known to increase the absorption of drugs from the mucosal membranes by increasing the residence time in the mucous and enhancing the permeability of drugs (see Khutoryanskiy V.V. Advances in mucoadhesion and mucoadhesive polymers. Macromolecular bioscience, (2011) 11(6), pp 748-64). Despite the attractive functional properties of CS making it suitable for many uses, there are some problems associated with its in vivo applications, such as high viscosity, high molecular weight, large aggregation formation and low solubility at physiological pHs (7.2-7.4) (see Rossi et al. Thermally sensitive gels based on chitosan derivatives for the treatment of oral mucositis. European journal of pharmaceutics and biopharmaceutics: Official Journal of Arbeitsgemeinschaft für Pharmazeutische Verfahrenstechnik e.V, 74(2) (2010), pp 248-54).